1. Field of the Invention
The present invention relates to a method for manufacturing a golf club.
2. Prior Art
As disclosed in Japanese Registered Patent Publication No.2560272, it is known art to provide an iron golf club which comprises a face member; a head body having an aperture on a front surface for securing the face member thereto, a cavity on a rear surface and a shaft attachment portion on one side; and a shaft connected thereto.
Recently, the main currents of iron golf clubs have been directed to the use of a cavity-back type head. The cavity-back configuration is aimed at enlarging a moment of inertia by concaving a middle portion of a rear face of a head so as to distribute the weight toward a periphery thereof, thus decreasing the deviation of traveling directions of balls caused by so-called off-center shots. According to conventional golf clubs, club heads are relatively long in the toe-to-heel direction, and thus, cavities thereof eventually become too long in the same direction, so that there is a problem that it is difficult to obtain a great repulsive force by resiliently bending a face of the head.
Further, an improved cavity-back type head with an undercut configuration is also known art. Such undercut configuration is aimed at making the center of gravity deeper by further hollowing a cavity toward the sole direction, which also contributes to enlarging a resiliently bending area on a face, improving a repulsive force against balls.
For methods of manufacturing a head with such undercut configuration, an insert die method wherein an insert die is used as a partial die for a cavity forming portion, a machining method wherein a golf club with a face on a front surface and a cavity on a rear surface is produced by machining, said cavity being machined from a rear side to form the undercut configuration.
According to conventional methods, however, there are limitations to the depth and configuration to be hollowed. Namely, according to the insert die method, the insert die must be removed after forming, but too deep undercut disenables the removal of the insert die. Further, according to the machining method in which machining is performed from a rear surface of a head, machining tools such drills often do not reach the depth of a cavity and is likely to damage other portions. In other words, according to these conventional methods, the undercut configuration is not free to form, thus leading to the restricted degree of freedom relative to the positional setting of the center of gravity of a head, making it difficult to insure an effective configuration and area on a face which is to be resiliently bent.
Further, iron golf clubs with a faceplate joined to a head body also have been known art. For example, as shown in FIG. 20, a head 51 may comprise a face portion 53 as a faceplate forming a front face 52 and a head body 55 provided with a shaft connecting portion 54 on one side. The surface of the face 52 of the head body 55 is formed with a recess portion 56 for fitting the face portion 53 therein by machining. After fitting the face portion 53 into the recess portion 53, a joint portion 57 on the surface of the face 52 is welded, so that the face portion 53 and the head body 55 are joined together.
In that case, however, it is imperative to precisely machine the recess portion 56 on the head body 55 so that the face portion 53 may be fitted into the recess portion 56 without a gap. Therefore, higher degree of precision in machining has been required. Further, due to the joint portion 57 being present on the surface of the face 52, there have been constraints that score lines 58 must be formed only inside of the joint portion 57. Moreover, the appearance of the face 52 has been impaired due to the presence of the joint portion 57 on the surface of the face 52. Still further, when forming the recess portion 56, there has been a problem that a gap is prone to be formed in a portion where a rear surface of the face portion 53 abuts against a front surface of the head body 55.
Accordingly, it is a main object of the present invention to provide method for manufacturing a golf club with a larger degree of freedom in designing the same so that a face may be easily bent resiliently and a head may have a lowered center of gravity.
It is another object of the present invention to provide a golf club with a face portion joined to a head body, which is easy to machine, free from a gap formed in a portion where the face portion abuts against the head body, subject to no positional constraints when forming score lines, and excellent in appearance of a face surface.
To attain the above objects, there is provided, in accordance with a first aspect of the invention, a method for manufacturing a golf club, the golf club comprising: a face member; a head body having an aperture on a front surface for securing the face member thereto a cavity formed on a rear surface and a shaft attachment portion at one side; and a shaft connected to the head body, the method comprising the steps of:
inserting a mechanical processing unit from a front side of the head body through the aperture to process an inner lower surface of the cavity to form an undercut portion formed by concaving a front side of the inner surface downwards; and then,
securing the face member to the aperture by means of laser beam welding or the like.
According to another aspect of the invention, there is provided a method for manufacturing a golf club, the golf club comprising: a face member, a head body having an aperture on a front surface for securing the face member, a hollow interior on a rear and a shaft connected to the head body, the method comprises the steps of:
inserting a mechanical processing unit from a front side of the head body through the aperture to form an undercut portion by concaving a front side of an inner lower surface of the hollow interior downwards; and then,
securing the face member to the aperture by means of laser beam welding,
According to the method, a mechanical processing unit can be inserted deep into the aperture without being disturbed by other portions when forming the undercut portion, and thus the degree of freedom with respect to machine processing can be enhanced and the undercut portion can be formed deeper. As a result, the configuration and area of the face are subjected to no restrictions associated with the forming of the undercut portion.
Also according to the method, as it is possible to form the undercut portion deeper, there can be provided a high performance golf club having such a deepened center of gravity and an enlarged sweet area and thus allowing golf balls to be raised more easily. Furthermore, as the undercut portion is formed by deeply concaving a front side of an inner lower surface of the cavity downwards, it is possible to reduce an area for a rear face of the face member to contact the head body. Thus, it is possible to warp or bent the face more efficiently, so that a greater repulsive force is developed to elongate traveling distances of balls.
According to a further aspect of the invention, there is provided a method for manufacturing a golf club, the golf club comprising: a head and a shaft connected to the head, the head being provided with a face on a front surface and a shaft connecting portion on one side, the method comprising the step of joining a face portion that is to form the face to a head body that is to be joined to a rear surface of the face portion by laser welding a peripheral edge portion of the head body.
According to the method, there can be provided a golf club which is easy to machine, free from a gap formed in a portion where the face portion abuts against the head body, subject to no positional constraints when forming score lines, and excellent in appearance of a face surface.